When Lee Sung-kyoung put on a few kilograms for her role as a weightlifting trainee, she was “a little depressed” to find patches of dry skin and stretch marks throughout her body.

“The best way to put on weight was to eat late at night and go straight to bed,” said the model-turned-actress at an interview at a cafe in Hapjeong-dong, Seoul, Thursday. “My face would be puffy the next morning.”

But the toll the extra weight posed on her health was forgotten once she began filming “Weightlifting Fairy Kim Bok-joo,” said Lee. The drama’s 16-episode run ended Wednesday on MBC.

“I found happiness in the innocence of the show. I felt like all of my complicated thoughts were filtered clean, and I was left only with the nicest feelings.”

A youthful tale of on-campus romance between two athletes in training, the series gained a devoted following among viewers who found respite in the freshness of puppy love and the sincerity of the dialogue, penned by Yang Hee-seung and Kim Soo-jin.

“(Writer Yang) did such a great job in capturing youth,” said Lee, 26. “She herself is very gentle. That sensitivity shows through.”

Model-actress Lee Sung-kyung poses for a photo before an interview at Cafe Kkumer in Hapjeong-dong, Seoul, Thursday. (YG Entertainment)

Lee plays spunky university student Bok-joo, whose daily routine consists of little more than eating and lifting weights until she falls in love for the first time. Unexpectedly, her object of affection is the lean-bodied swimmer Joon-hyung, played by Nam Joo-hyuk, who has a track record of dating only the skinniest, “most attractive” girls. But he, too, soon falls for the loveable, round-faced Bok-joo.

“Everyone has a youth. It’s a time when people shine more brightly even if they stumble,” the 24-year-old Bok-joo says in a voiceover in the show’s finale. “Right now, with nothing to lose, and everything to gain, more excited than ever. ... I’m still imperfect but in some way, couldn’t be more perfect.”

At times, Bok-joo wonders if she and athletes in similar sports are destined to “give up on their lives as women.”

“The social perception is that people are in awe of such women, but they’re not regarded as traditionally beautiful,” said Lee. “In this show, I was so happy to see how charming and loved Bok-joo is.”

Lee began modeling in 2008 before shifting her focus to acting in 2014. After having experienced two nearly opposite worlds in terms of her body figure, Lee said both modeling and weightlifting were intense careers that required passion to overcome their difficulties.

“In modeling, you have to be scouted for shows. In weightlifting, you have to win medals,” said Lee.

“There can be stress amid the competition.

“But as a professor says in the show, ‘You have to feel sheer happiness by lifting up that piece of metal.’”

“Weightlifting Fairy” is available outside Korea on streaming sites DramaFever and Viki.